The embossing of webs, such as paper webs, is well known in the art. Embossing of webs can provide improvements to the web such as increased bulk, improved water holding capacity, improved aesthetics and other benefits. Both single ply and multiple ply (or multi-ply) webs are known in the art and can be embossed. Multi-ply paper webs are webs that include at least two plies superimposed in face-to-face relationship to form a laminate.
During a typical embossing process, a web is fed through a nip formed between juxtaposed generally axially parallel rolls. Embossing elements on the rolls compress and/or deform the web. If a multi-ply product is being formed, two or more plies are fed through the nip and regions of each ply are brought into a contacting relationship with the opposing ply. The embossed regions of the plies may produce an aesthetic pattern and provide a means for joining and maintaining the plies in face-to-face contacting relationship.
Embossing is typically performed by one of two processes; knob-to-knob embossing or nested embossing. Knob-to-knob embossing typically consists of generally axially parallel rolls juxtaposed to form a nip between the embossing elements on opposing rolls. Nested embossing typically consists of embossing elements of one roll meshed between the embossing elements of the other roll. Examples of knob-to-knob embossing and nested embossing are illustrated in the prior art by U.S. Pat. Nos. 3,414,459 issued Dec. 3, 1968 to Wells; 3,547,723 issued Dec. 15, 1970 to Gresham; 3,556,907 issued Jan. 19, 1971 to Nystrand; 3,708,366 issued Jan. 2, 1973 to Donnelly; 3,738,905 issued Jun. 12, 1973 to Thomas; 3,867,225 issued Feb. 18, 1975 to Nystrand; 4,483,728 issued Nov. 20, 1984 to Bauernfeind; 5,468,323 issued Nov. 21, 1995 to McNeil; 6,086,715 issued Jun. 11, 2000 to McNeil; 6,277,466 Aug. 21, 2001; 6,395,133 issued May 28, 2002 and 6,846,172 B2 issued to Vaughn et al. on Jan. 25, 2005.
Knob-to-knob embossing generally produces a web comprising pillowed regions which can enhance the thickness of the product. However, the pillows have a tendency to collapse under pressure due to lack of support. Consequently, the thickness benefit is typically lost during the balance of the converting operation and subsequent packaging, diminishing the quilted appearance and/or thickness benefit sought by the embossing.
Nested embossing has proven in some cases to be a more desirable process for producing products exhibiting a softer, more quilted appearance that can be maintained throughout the balance of the converting process, including packaging. With nested embossing of a multi-ply product, one ply has a male pattern, while the other ply has a female pattern. As the two plies travel through the nip of the embossing rolls, the patterns are meshed together. Nested embossing aligns the knob crests on the male embossing roll with the low areas on the female embossing roll. As a result, the embossed sites produced on one ply provide support for the embossed sites on the other ply.
Another type of embossing, deep-nested embossing, has been developed and used to provide unique characteristics to the embossed web. Deep-nested embossing refers to embossing that utilizes paired emboss elements, wherein the protrusions from the different embossing elements are coordinated such that the protrusions of one embossing element fit into the space between the protrusions of the other embossing element. Although many deep-nested embossing processes are configured such that the embossing elements of the opposing embossing members do not touch each other or the surface of the opposing embossing member, embodiments are contemplated wherein the deep-nested embossing process includes tolerance such that the embossing elements touch each other or the surface of the opposing embossing member when engaged. (Of course, in the actual process, the embossing members generally do not touch each other or the opposing embossing member because the web is disposed between the embossing members.) Exemplary deep-nested embossing techniques are described in U.S. Pat. No. 5,686,168 issued to Laurent et al. on Nov. 11, 1997; U.S. Pat. No. 5,294,475 issued to McNeil on Mar. 15, 1994; U.S. patent application Ser. No. 11/059,986; U.S. patent application Ser. No. 10/700,131 and U.S. Patent Provisional Application Ser. No. 60/573,727.
While these deep-nesting technologies have been useful, it has been observed that when producing certain deep-nested embossed patterns, the resulting web can lose some of its strength and/or softness due to the embossing process. Also, some deep-nested embossing patterns can substantially weaken the web or even tear it while the web is being embossed. Further, the deep-nested embossing patterns can, in some cases, actually detract from the acceptance of the product by making the product appear somewhat rough or stiff.
Accordingly, it would be desirable to provide a deep-nested embossing apparatus and/or process that provides at least some of the benefits of the prior art deep-nested embossing methods while reducing at least some of the negatives that can be associated with such processes. For example, it may be desirable to provide a deep-nested embossing apparatus and method for deep-nested embossing a web that provides improved softness over the prior art deep-nested embossing methods. Further, it may be desirable to provide a deep-nested embossing apparatus and/or process that provides a more aesthetically pleasing pattern to the embossed web. Further, it may be desirable to provide a deep-nested embossing apparatus and/or process that provides less damage to the web as prior art deep-embossing apparatuses and methods. Further yet, it may be desirable to provide a web of material that has been subjected to the improved deep-nested embossing process.